Incandescent lamp and method of manufacture



G. K. DANKO ETAL INCANDESCENT LAMP AND METHOD OF MANUFACTURE Dec. 1, 1970 Filed Nov. 17. 1967 2 Sheets-Sheet 1 lnven tor's. GeoTgn e K. Danko Fredevick A. Mosbg 9 0% The' Dec. 1,1910

INCANDESCENT LAMP AND METHOD Filed NOV. 17 1967 Fig 7.

G. K. DANKO ET AL OF MANUFACTURE 2 Sheets-Sheet 2 lnven tovg: George H. Danko Fw'edar'ick A. Mosbg United States Patent 3,544,188 INCANDESCENT LAMP AND METHOD OF MANUFACTURE George K. Danko, Chesterland, and Frederick A. Mosby,

Cleveland, Ohio, assignors to General Electric Company, a corporation of New York Filed Nov. 17, 1967, Ser. No. 683,936

Int. Cl. H01j 9/ 38 US. Cl. 316 6 Claims ABSTRACT OF THE DISCLOSURE A single-ended pinch seal lamp is made by first pinch sealing an end of an exhaust tube as well as a portion of a support wire in one end of a tubular envelope of vitreous material. The support wire is used to support a coiled filament having leads attached to its ends and permits stretching the coiled filament while the leads are pinch sealed in the other end of the tubular envelope, after which the envelope may be exhausted and filled with gas through the exhaust tube which is then tipped off.

BACKGROUND OF THE INVENTION Field of the invention The invention relates generally to electric incandescent lamps, and more particularly to a construction and method of assembly of the filament supporting structure.

Description of the prior art The invention has particular application to incandescent lamps of the halogen regenerative cycle type wherein a coiled tungsten wire filament is enclosed in a compact envelope of essentially fused silica or quartz glass, and still more particularly to single-ended type lamps wherein both of the current supply or lead-in conductors, which usually include an extremely thin molybdenum foil section, are sealed through the same end of the envelope. It is sometimes desirable to support the coiled filament at a point intermediate its ends, and in some cases in a manner such that the coil is stretched when cold in order to avoid buckling or distortion when it is heated during operation. In some cases this has been accomplished by the use of a special quartz bridge construction which is fused across the lead wires above the fragile foil portions and which also carries a support wire for the filament. In other cases, filament support wires have been, in turn, supported from the pinch seal, as for example in Pat. 3,270,238 to F. A. Mosby.

SUMMARY OF THE INVENTION It is an object of the invention to provide a simplified and highly effective construction and method of assembly of the filament and its supporting structure.

In accordance with one aspect of the invention, a portion of a support wire member and an exhaust tube are pinch sealed in one end of a tubular envelope, and the lead-in conductors for the filament are pinch sealed in the other end of the envelope while the filament is supported from the said support wire which was previously pinch sealed in the first-mentioned end of the envelope. In addition to supporting the filament coil in the finished lamp, the support wire may be used to hold a portion of the filament coil while it is stretched during the second pinch sealing.

In accordance with another aspect of the invention the exhaust tube may be used to support the filament support wire member while it is sealed in the said one end of the envelope along with the exhaust tube, and the envelope is subsequently exhausted and filled with a desired atmosphere through the said exhaust tube.

BRIEF DESCRIPTION OF THE DRAWING In the drawing,

FIGS. 1 to 5 are elevations showing steps in the manufacture of a lamp in accordance with the invention, FIG. 5 also showing the finished lamp;

FIG. 6 is an elevation of a modified form of lamp;

FIG. 7 is a perspective view of the filament support wire member in the FIG. 6 lamp;

FIG. 8 is an elevation illustrating the assembly of the support wire with the envelope; and

FIG. 9 is a fragmentary elevation, partly in section and on an enlarged scale, of a holder member for the support wire as used in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawing, assembly of the lamp may be started by inserting into a suitable chuck or holder 1, an exhaust tube 2 of vitreous material which may be essentially fused silica or quartz glass including the material referred to as 96% fused silica and also known as Vycor. As here illustrated, the exhaust tube 2 is used to hold a support wire member 3 which is in this case made of refractory metal, preferably tungsten. The

support wire 3 is formed with a hairpin-shaped stem portion 4 having its closed bight end uppermost and bent to a hook shape 5 and with its leg portions extending downward into the exhaust tube 2 where they are bent to extend first upwardly, at -6, and then over the upper edge of the exhaust tube and divergently downward at their free ends 7.

As shown in FIG. 2, a quartz tubular envelope 8 is held in coaxial vertical alignment with the exhaust tube 2 and with its lower end surrounding the upper end of the exhaust tube and with the end portions 7 of the support wire member terminating well within the envelope 8. The envelope 8 is preferably closed temporarily at its upper end by a cap member 9, and a flow of inert gas such as nitrogen is started upwardly through the exhaust tube 2 by way of an axial bore 10 in exhaust tube holder 1. The tube 2 fits in a larger bore 11 which accommodates the exhaust tube 2, the lower end of which rests on a shoulder 12 formed by the reduction in size from bore 11 to bore 10. The lower end of the envelope 8 is heated and softened by burners 13, during which the enclosed upper end of exhaust tube 2 is also heated by radiation and conduction, and the tungsten wire support 3 is protected against oxidation by the flow of inert gas.

The softened lower end of envelope 8 is then pinched in known manner by a pair of jaws having relieved or notched faces which avoid pinching shut the exhaust tube 2 while fusing it in the flattened pinch seal 14 (FIG. 3) which otherwise seals the lower end of the envelope 8 and in which are embedded the ends 7 of the support wire member 3.

As shown in FIG. 4, the envelope 8 is then inverted with a filament assembly hung fromthe hook of the support 3. As herein illustrated by Way of example, the filament assembly comprises a generally U-shaped tungsten wire filament 15 having coiled-coil segments 16 connected at the center by a single coiled bend or bight portion 17 which is engaged by the hook 5. Single coiled ends or legs 18 of the filament firmly enclose and are attached to wires 21 of refractory metal such as molybdenum which are held in deep holes or wells 22 in the lead wire chuck or holder 1a. The outer leads 21 are firmly held in holder 1 in any suitable manner, as by screws or spring-loaded pins, for example, in such position relative to the envelope 8 that the filament coils 16 are preferably stretched slightly.in1order to avoid buckling or sagging when they are highly heated in normal operation of the lamp.

A flow of nitrogen gas is started downward through the exhaust tube 2 and envelope 8, and the lower end of envelope 8 is then heated and softened by burners 24, and then compressed by suitable jaws to form the flattened pinch seal 23 (FIG. 5) to hermetically seal the foil sections 20 and to embed adjacent portions of the inner and outer leads 19 and 21 and, optionally, toalso embed a part of the lower end of the filament legs 18.

It will be understood that in practice the burners 13 and 24, as well as the pinch jaws, are arranged in positions rotated ninety degrees from those shown in FIGS. 2 and 4, that is, normal to the plane containing the ends 7 of the support wire member 3 and also the foils 20.

The'lamp may then be completed by exhausting the envelope 8 through exhaust tube 2 and filling it with a suitable atmosphere such as an inert gas like nitrogen, argon, krypton or xenon or mixtures thereof, plus a small As shown herein, the supportwire member is supported by the lower end of a metal rod which extends axially of envelope 8 from a cap member 31 which rests on, and closes off, the upper end of said envelope 8. As shown more clearly in FIG. 9, the hook 26 and stem portion 27. are shaped to be slightly compressed and held securely by friction in a hole or bore 32in the end of rod 30. The support wire member 25 is also properly oriented for the pinch sealing operation, by providing longitudinal slots 33 inrod 30 through which extend the sections of portions of the legs 29 of support 25. p

As described in connection with FIGS. 2 and 3, an inert gas flow is introduced into envelope 8 through exhaust tube 2 by way of bore 10 in holder 1, and the lower end of envelope 8 is heated and softened and then pinch sealed to form the seal 14 (FIG. 6) which closes ofl" the end of envelope 1 around the exhaust tube 2 and embeds portions of the legs 29 of support 25.

The assembly of filament 15 (FIG. 6) and lead-in conductors 19, 20, 21 is then supported from hook 26 of support 25, preferably with the filament coils 16 slightly stretched, and the pinch seal 23 is formed as described in connection with FIGS. 4 and 5, after which the envelope 8. is exhausted and filled with the desired atmosphere quantity of halogen such as iodine or bromine, or compounds thereof such as hydrogen bromide or a hydrocarbon compound of bromine as is now well known in the art. The exhaust tube 2 is then sealed or tipped ofi as illustrated by broken lines at 2a.

The compactness of such a lamp of the halogen cycle type may be illustrated by an example wherein a 500 watt, 120 volt lamp is made in a fused quartz envelope 8 having an inside diameter of about 15 millimeters and an internal length (between seals 14 and 23) of about 28 millimeters.

In FIGS. 6 to 9, the same reference numerals are used as for corresponding parts in FIGS. 1 to 5. The lamp of FIG. 6 is the same as that of FIG. 5 except for the diflEerent form of the filament support wire member 25 which is also shown in FIG. 7 and which is preferably formed from tungsten wire. In this case the hook 26 is at the end of a short hairpin-shaped stem portion 27 which extends from the center of the base portions 28 of the generally U-shaped support 25 which has the ends of its legs 29 embedded in-the pinch seal 14.

As in FIG. 4, the hook 26 engages the bend or loop portion 17 between the coiled-coil segments 16 of the U- shaped filament 15 which has single coiled legs 18 which enclose and are attached'to inner leads 19 which are.

stretched conditiomThe envelope 8 is evacuated and filled with a desired atmosphere through exhaust tube 2 which is open through the pinch seal 14, and which is subsequently tipped oiT as shown at 2a.

In assembling the FIG. 6 lamp, the exhaust tube 2 is held in the chuck or holder 1, as shown in FIG. 8 which corresponds to FIG. 2, and the tubular envelope 8 is held slightly above the upper surface of holder 1 with its lower end surrounding the upper end of the exhaust tube 2. The support wire member 25 is held in suitable manner with its base portion 28 and hook 26 above the upper end of exhaust tube 2 and itslegs 29 extending longitudinally of the space between the. tube 2 and the envelope 8 and terminating well within the envelope 8.

through exhaust tube 2 which is then tipped off at 2a.

What we claim as new and desire to secure by Letters Patent of the ,United States is:

1. The method of manufacture of an incandescent lamp which comprises pinch sealing one end of an exhaust tube and a portion of an auxiliary support wire member in one end of a tubular envelope of vitreous material while maintaining an opening through said exhaust tube to the interior of said envelope and with a portion of said support wire projecting into the interior of the envelope from end portions which terminate wholly within the resulting pinch seal, and subsequently, with said support wire member engaging a portion of a helically coiled filament and with a pair of lead-in conductors connected to respective ends of said filament, said conductors extending outwardly through the other end of said tubular envelope, pinch sealing the said other end of the envelope to close it and to hermetically seal therein portions of said lead-in conductors,

I and then replacing the air in said envelope with a desired atmospheric environment through said exhaust tube and sealing off said exhaust tube.

2. The method of claim 1 wherein the support wire member is shaped to provide a portion which extends into the interior of and is supported by the exhaust tube during the first said pinch sealing.

3. The method of claim 1 wherein, during the first pinch sealing, the exhaust tube and tubular envelope are vertically disposed with the upper end of the exhaust tube extending into the lower end of the tubular envelope and wherein the support wire member has a hairpin-shaped stem portion with its closed bight end above the end of the exhaust tube and bent to a hook shape and with its leg portions extending downward into the exhaust tube where they are bent to extend first upwardly toward and then over the upper edge of the exhaust tubeand divergently downward to terminate within the tubular envelope and have portions thereof embedded in said firstpinch seal, and wherein the hook-shaped portion of said support wire is caused to engage the mid-portion of the coiled filament which is of generally U-shaped form with the said lead-in conductors connected to the free ends thereof.

4. The method of claim 3 wherein said lead-in conductors and said envelope are held in relative longitudinal relationship such that the coiled leg portions of said U- shaped filament are in a slightly stretched condition at the time the said other end of the envelope is pinch sealed. 5. The method of claim 1 wherein, during the first pinch sealing, the support wire member is supported with free end leg portions thereof extending generally longitudinally of and at opposite sides of the exhaust tube and ter minating within the tubular envelope to have portions thereof embedded wholly within said first pinch seal, said support wire member also including a portion joining said leg portions and including a hook-shaped portion in the interior of said envelope, and wherein said hook-shaped portion of said support wire is caused to engage the midportion of the coiled filament which is of generally U- shaped form with the said lead-in conductors connected to the free ends thereof.

6. The method of claim 5 wherein said lead-in conductors and said envelope are held in relative longitudinal relationship such that the coiled leg portions of said U-shaped filament are in a slightly stretched condition at the time the said other end of the envelope is pinch s al d,

6 References Cited UNITED STATES PATENTS JOHN F. CAMPBELL, Primary Examiner 0 R. J. CRAIG, Assistant Examiner US. Cl. X.R. 

